Loans and Allowance for Credit Losses (Aging Analysis of Past Due Loans by Portfolio Class) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 21,134,282	$ 21,789,931
Recorded Investment > 90 Days and Accruing	5,524	3,361
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	42,102	56,684
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	12,348	19,269
Greater Than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	37,284	100,538
Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	91,734	176,491
Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	21,042,548	21,613,440
Total Commercial [Member] | Commercial Real Estate - Income Producing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	3,464,626	3,357,939
Recorded Investment > 90 Days and Accruing		182
Total Commercial [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,228,670	1,065,057
Recorded Investment > 90 Days and Accruing	83
Total Commercial [Member] | 30-59 Days Past Due [Member] | Commercial Real Estate - Income Producing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	281	1,494
Total Commercial [Member] | 30-59 Days Past Due [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,624	4,168
Total Commercial [Member] | 60-89 Days Past Due [Member] | Commercial Real Estate - Income Producing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	107	798
Total Commercial [Member] | 60-89 Days Past Due [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,022	284
Total Commercial [Member] | Greater Than 90 Days Past Due [Member] | Commercial Real Estate - Income Producing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	5,307	5,744
Total Commercial [Member] | Greater Than 90 Days Past Due [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	587	2,001
Total Commercial [Member] | Total Past Due [Member] | Commercial Real Estate - Income Producing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	5,695	8,036
Total Commercial [Member] | Total Past Due [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	4,233	6,453
Total Commercial [Member] | Current [Member] | Commercial Real Estate - Income Producing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	3,458,931	3,349,903
Total Commercial [Member] | Current [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,224,437	1,058,604
Total Commercial [Member] | Total Commercial And Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	12,433,706	12,844,428
Recorded Investment > 90 Days and Accruing	2,960	1,538
Total Commercial [Member] | Total Commercial And Industrial [Member] | Commercial Non-Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	9,612,460	9,986,983
Recorded Investment > 90 Days and Accruing	2,818	583
Total Commercial [Member] | Total Commercial And Industrial [Member] | Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,821,246	2,857,445
Recorded Investment > 90 Days and Accruing	142	955
Total Commercial [Member] | Total Commercial And Industrial [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	9,085	9,488
Total Commercial [Member] | Total Commercial And Industrial [Member] | 30-59 Days Past Due [Member] | Commercial Non-Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	8,381	7,963
Total Commercial [Member] | Total Commercial And Industrial [Member] | 30-59 Days Past Due [Member] | Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	704	1,525
Total Commercial [Member] | Total Commercial And Industrial [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	3,776	3,317
Total Commercial [Member] | Total Commercial And Industrial [Member] | 60-89 Days Past Due [Member] | Commercial Non-Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	3,123	2,564
Total Commercial [Member] | Total Commercial And Industrial [Member] | 60-89 Days Past Due [Member] | Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	653	753
Total Commercial [Member] | Total Commercial And Industrial [Member] | Greater Than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	8,604	53,193
Total Commercial [Member] | Total Commercial And Industrial [Member] | Greater Than 90 Days Past Due [Member] | Commercial Non-Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	7,041	39,530
Total Commercial [Member] | Total Commercial And Industrial [Member] | Greater Than 90 Days Past Due [Member] | Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,563	13,663
Total Commercial [Member] | Total Commercial And Industrial [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	21,465	65,998
Total Commercial [Member] | Total Commercial And Industrial [Member] | Total Past Due [Member] | Commercial Non-Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	18,545	50,057
Total Commercial [Member] | Total Commercial And Industrial [Member] | Total Past Due [Member] | Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,920	15,941
Total Commercial [Member] | Total Commercial And Industrial [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	12,412,241	12,778,430
Total Commercial [Member] | Total Commercial And Industrial [Member] | Current [Member] | Commercial Non-Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	9,593,915	9,936,926
Total Commercial [Member] | Total Commercial And Industrial [Member] | Current [Member] | Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,818,326	2,841,504
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,423,890	2,665,212
Recorded Investment > 90 Days and Accruing	310	912
Residential Mortgages [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	23,306	29,319
Residential Mortgages [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	4,638	9,858
Residential Mortgages [Member] | Greater Than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	15,339	27,886
Residential Mortgages [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	43,283	67,063
Residential Mortgages [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,380,607	2,598,149
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,583,390	1,857,295
Recorded Investment > 90 Days and Accruing	2,171	729
Consumer [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	6,806	12,215
Consumer [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,805	5,012
Consumer [Member] | Greater Than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	7,447	11,714
Consumer [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	17,058	28,941
Consumer [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 1,566,332	$ 1,828,354